The project starts out by pulling apart an electronic scissor jack to get access to the solder pads for the up and down buttons. Once wires are added there, a servo is the next victim. [Windell] recommends using an old servo with a busted motor, but you can use a good one just the same. The servo’s pots are replaced with 10 turn pots, and then wired up to a controller board, to which the jack is also connected. Then, to provide feedback to the servo, a string is looped around the top of the jack, which is used to turn the pots added in the previous step.

[Windell] says that the setup works quite well, though we imagine the duty cycle might be a bit short before adjustments are required. Regardless, it’s a quick way to get a heavy load lifted with servo precision.

I’ve always liked scissor jacks, because you can get them at the junkyard for peanuts, and they can be blasted up and down with an air wrench… Unfortunately they wear out quickly in this sort of duty. I wonder if that will be a problem here.

@raidscsi The problem with a rotary encoder is that you would only be able to know the rotation, not the actual position. You would either always have to start the control with jack at the lowest point or store the position in memory. with a pot you can just read the position at powerup.

Why not just attach the pot directly to the pivot joint of the jack, or even just use a small arm as used on car/truck air suspension sensors? I can’t see you need a 10-turn-pot’s worth of accuracy from your bit of string & elastic band.